The proposed 5-year project determines late functional consequences of iron deficiency anemia in infancy. Iron deficiency anemia is the most common single nutrient deficiency in the world, affecting 25% of the world's infants. It is associated with lower mental and motor test scores among infants and with alterations in attention and affect. Lower test scores are still present at five years of age, despite correction of the anemia with iron therapy in infancy. However, the functional significance of these findings is unknown. The proposed project will assess functional consequences of early iron deficiency by following over the next five years a group of 11- to l2-year-old Costa Rican children whose iron status and development were determined in infancy and at five years of age. Functional effects will be assessed in cognitive, motor, scholastic, behavioral, and physical domains. A comprehensive neurodevelopmental and motor test battery will be used to pursue differences identified at age five years, specifically greater difficulty with tasks requiring spatial, visual-motor, and motor skills. Detailed tests of attention will also be included, since more attention problems were reported for formerly anemic children at age five. The children's school performance will also be followed for the next five years, monitoring grade retention, school drop- out, special education, academic v. vocational tracking, as well as grades, achievement test scores, awards, and honors. A set of behavioral measures will be used to evaluate the hesitance and wariness observed among the formerly anemic children as infants and the increase in internalizing problems noted among them at age five. Long-term physical sequelae related to pubertal progression and dental enamel defects will be determined. The proposed project will also pursue other provocative findings in this sample of children, specifically stable individual differences in serum prolactin levels (a stress-responsive hormone, which is altered in iron deficiency) and a relationship between serum prolactin levels and unhappy, hesitant behavior.